Biomass gasification device

ABSTRACT

The biomass gasification device described in this embodiment is equipped with temporary holding sections ( 10 )( 20 ) that temporarily hold and discharge heat carriers ( 30 ). The temporary holding section has a vessel ( 111 )( 121 ) and a discharge section ( 119 )( 129 ) for discharging the heat carriers. A baffle ( 115 )( 125 ) within the vessel ( 111 )( 121 ) is provided to form a gap between the main body of the baffle and the interior side wall of the vessel, for the heat carriers ( 30 ) to pass through. Alternatively, piping ( 131 )( 141 ) may be provided on the interior side walls of the vessel ( 111 )( 121 ) for passage of the heat carriers.

TECHNICAL FIELD

This invention involves a biomass gasification device which utilizesheat carriers.

BACKGROUND ART

As a gasifier for biomass with high ash content (e.g., sewage sludgecontaining 20% ash by weight) can be dried and then pyrolyzed in anair-blown fluidized bed pyrolyzer operating at a temperature range of500 to 800° C. The pyrolysis gas is combusted with air at a hightemperature (in the range of 1,000 to 1,250° C.) and the heat producedis used to generate steam for turbine power generation (JapaneseUnexamined Patent Application Publication No. 2002-32-2902). Thepyrolysis of biomass with high ash content at temperatures in the rangeof 450 to 850° C. in an air-blown circulating fluidized bed vessel isalso used to generate turbine power. On the other hand, the pyrolysisgas containing tar is reformed under the presence of oxygen attemperatures in the range of 1,000 to 1,200° C. (Japanese UnexaminedPatent Application Publication No. 2004-51-745). To prevent the flowingheat carriers from sticking to one another, in a similar way asdescribed above, the pyrolysis residue (also referred to as char) isseparated from the heat carriers via pyrolysis and is recovered using acyclone. After that, the char is granulated and then fed into thecirculating fluidized reforming vessel, in which it is sintered at atemperature in the range of 900 to 1000° C. (Japanese Granted PatentPublication No. 4155507).

Moreover, in this embodiment, a medium for carrying heat (referred to asheat carrier), a preheater which supplies heat to the heat carriers, areformer in which the steam methane reforming of the pyrolysis gasoccurs, a pyrolyzer which thermally decomposes the raw material (i.e.,woody biomass), a char separator which separates the char from the heatcarriers, and a hot-air furnace which generates hot air by burning thechar produced, are described (Japanese Unexamined Patent ApplicationPublication No.

In addition, a facility is proposed which is characterized by twoindependent apparatus comprising of a pyrolyzer which operates in thethermal decomposition zone, and a reformer which operates in thereaction zone. These may either be connected in series or in parallel.The heat carrier passes through a heating zone (approximately 1100° C.),a reaction zone (in the range of 950 to 1000° C.), a thermaldecomposition zone (in the range of 550 to 650° C.) followed by a charseparation stage, and subsequently returns to the heating zone. Thechar, which was obtained from its separation from the heat carriersexiting the pyrolyzer, is burned in a combustion device to generate aheat-decomposed coke. There is a previously described method forproducing gas with high calorific value from an organic substance or itsmixture by heating the heat carriers in a heating zone, utilizingsensible heat (Japanese Granted Patent Publication No. 4264525).

Furthermore, the pyrolysis gas is introduced from the pyrolyzer to apyrolysis gas reformer. A gasification method in which a pipe allowingthe introduction of pyrolysis gas is installed on the side of thepyrolyzer, below the top of the preheated heat carriers has also beenpreviously described (Japanese Unexamined Patent Application PublicationNo. 2019-65160).

SUMMARY OF THE INVENTION Problem to be Solved by the Invention

In the conventional arrangement, the spherical ceramic balls, whichserves as heat carriers in the preheater and the pyrolyzer, can becomerestricted, preventing it from flowing, hence, becoming stagnant.

Considering this, the present invention describes a biomass gasificationdevice that allows the heat carriers to move smoothly within atemporary-holding vessel such as a preheater or a pyrolyzer.

Means to Solve the Problem

A biomass gasification device according to the present inventioncomprises:

a vessel;a baffle provided within the vessel;and an outlet provided below the baffle to discharge the heat carriers.A gap for allowing the heat carriers to pass through may be providedbetween the baffle and the interior side walls of the vessel. Otherwise,piping to allow the heat carriers to pass through the inner wall of theside part of the vessel may be provided.

In the biomass gasification device according to the present invention,the temporary holding vessel is a preheater that preheats the heatcarriers, and the outlet is the outlet of the preheater. The heatcarrier discharged from the preheater outlet may be fed to thepyrolyzer.

In the biomass gasification device according to the present invention,the temporary holding vessel is a pyrolyzer that receives a supply ofheat carriers preheated in a preheater. In the pyrolyzer, the pyrolysisof biomass occurs using with the heat input coming from the heatcarriers. The outlet is the pyrolyzer outlet. The heat carriersdischarged from the pyrolyzer outlet may be fed to the preheater througha recirculation system.

In the biomass gasification device according to the present invention,the upper surface of the baffle may have its central section positionedhigher than its peripheral section, and a sloping surface may beprovided between the central section and the peripheral section.

In the biomass gasification device according to the present invention,the bottom surface of the baffle may have its central section positionedlower than the peripheral region, and a sloping surface may be providedbetween its central section and its peripheral section.

In the biomass gasification device according to the present invention,several fixing members for fixing the main body of the baffle to theinterior side walls of the vessel are provided between the main body ofthe baffle and the interior side walls of the vessel. The gaps betweenthe fixing members may serve as spaces to allow passage of the heatcarriers towards the outlet.

In the biomass gasification device according to the present invention,the main body of the baffle is disk-shaped. The main body may be securedto the vessel by fixing members between the main body of the baffle andthe interior side walls of the vessel or by fixing members on the backside of the main body.

In the biomass gasification device according to the present invention,the vessel has an upper body and a lower body below the upper body,wherein the cross-section of the lower portion of the upper body issmaller than the cross-section of the upper end of the lower body. Thebaffle is provided below the lower end of the upper body and a gap maybe formed between the baffle and the lower body.

Effect of the Invention

In the present invention, in the case wherein a gap is provided betweenthe baffle and the interior side walls of the vessels for the heatcarriers to pass through, or in the case wherein piping is provided inthe interior side wall of the vessel for the heat carriers to passthrough, the heat carriers contained in the temporary holding section ofthe preheater, pyrolyzer, or similar vessels, can flow smoothly.

BRIEF DESCRIPTION OF DRAWINGS

FIG. 1 is a schematic diagram of the biomass gasification device.

FIG. 2 shows the distribution profile of the heat carriers before startof movement within a pyrolyzer in the actual implementation of thebiomass gasification device.

FIG. 3 shows the distribution profile of the heat carriers after thestart of movement within a pyrolyzer in a sample biomass gasificationdevice.

FIG. 4 shows the distribution profile of the heat carriers before startof movement within a pyrolyzer in the actual implementation of thebiomass gasification device.

FIG. 5 shows the distribution profile of the heat carriers after thestart of movement within the pyrolyzer (20) in the actual implementationof the biomass gasification device.

FIG. 6 shows an illustration of the baffle installed in the lowersection of the pyrolyzer in an actual implementation of the biomassgasification device.

FIG. 7 shows an illustration of the preheater in an actualimplementation of the biomass gasification device.

FIG. 8 shows an illustration of the pyrolyzer in an actualimplementation of the biomass gasification device.

FIG. 9 shows another view of the illustration of the preheater in anactual implementation of the biomass gasification device.

FIG. 10 shows another view of the illustration of the pyrolyzer in anactual implementation of the biomass gasification device.

FIG. 11 is a schematic diagram of another form of an actualimplementation of the biomass gasification device.

FIG. 12 is the top view of the baffle, showing the locations of thefixing members between the body of the baffle and the interior side wallof the vessel.

CONFIGURATIONS TO IMPLEMENT INVENTION

As shown in FIG. 1 , the biomass gasifier of this embodiment consists ofa preheater (10), which preheats the heat carriers (30); a pyrolyzer(20) (biomass pyrolyzer), which receives the heat carriers that werepreheated in the preheater (10); a pyrolysis gas reformer (40), in whichsteam methane reforming with partial oxidation of the pyrolysis gasgenerated by pyrolysis with air or oxygen occurs; and a control unitthat performs various operational controls (100) (see FIG. 11 ).

The heat carriers (30) (which may be also referred to as the heatcarrying medium) are composed of a plurality of granules and/or lumps,preferably made of one or more materials selected from the groupconsisting of metals and ceramics. As for the metals, there is apreference for iron, stainless steel, nickel alloy, and titanium alloy.There is higher preference for stainless steel. As for the ceramics,there is preference for alumina, silica, silicon carbide, tungstencarbide, zirconia, and silicon nitride. There is higher preference foralumina.

The shape of the heat carriers (30) is preferably spherical (ball), butdoes not necessarily have to be a perfect sphere; it can be a sphericalobject with an elliptical or ellipsoidal cross-section. The diameter(i.e., maximum diameter) of the spheres is preferably in the range of 3to 25 mm, more preferably in the range of 8 to 15 mm. If the upper limitof the diameter of the spherical material (25 mm) were exceeded, thereis high likelihood for the heat carriers to become stationary inside thepyrolyzer (20) and cause blockage. On the other hand, if the diameter ofthe spherical material were less than the lower limit (3 mm), tar anddust adhering to the spherical material in the pyrolyzer (20) may causethe spherical material to stick to each other and cause blockage. Forexample, if the diameter of the spherical material were less than 3 mm,the tar and dust adhering to the spheres may cause the spheres to alsoadhere to the inner walls of the pyrolyzer (20). In the worst case, theflow through the pyrolyzer (20) may be blocked. In addition, when thespherical materials with tar attached is pulled out through the valve atthe bottom of the pyrolyzer (20), due to the light weight of thespherical material that is less than 3 mm in diameter, and also due tothe tar attached to it, they may not fall naturally and stick to theinternals of the valve, resulting to blockage.

Biomass referred to in this embodiment refers to the so-called biomassresources. Biomass resources include plant biomass, such as thinnedwood, lumber waste, pruning, forest residues, and unutilized lumberdiscarded from the forestry industries; vegetable residues and fruittree residues discarded from agricultural industries; rice straw, wheatstraw, rice husks, marine plants, and construction waste wood;biological biomass, such as livestock waste and sewage sludge; andmiscellaneous domestic discharges, such as dust and food waste. Thisequipment described in this embodiment is preferably suitable forgasification of the described biomass resources. In any of the biomassresources, the ash content is preferably 5.0% or more (dry weightbasis), more preferably 10.0 to 30.0% (dry weight basis), and even morepreferably 15.0 to 20.0% (dry weight basis). In particular, theequipment described in this embodiment is suitable for the gasificationof high ash content biomass, especially sewage sludge and livestockwaste.

The heat carriers (30) that are preheated in the preheater (10), are fedto the pyrolyzer (20) by free fall from the preheater (10) via a valve.In the pyrolyzer (20), the heat from the heat carriers (30) induces thepyrolysis of the biomass fed into the pyrolyzer (20). The heat carriers(30) in the pyrolyzer (20) are discharged from the pyrolyzer (20) byfree fall through a valve and preferably recirculated back to thepreheater (10).

The biomass gasification device of the present embodiment has temporaryholding section (10)(20) for storing the supplied heat carriers (30) anddischarging the heat carriers (30). The temporary holding sections(10)(20) consists of: housings or vessels (111)(121); baffles (115)(125)which has a front surface, provided inside the housings (111)(121); andoutlet sections (119)(129) provided below the baffles (115)(125) fordischarging the heat carriers (30). The gap marked G in FIGS. 7 and 8may be provided between the internal side walls of (121) for the heatcarriers (30) to pass through.

In the present embodiment, as an example, the temporary holding sectionsrefer to a preheater (10) and a thermal decomposition device or apyrolyzer (20). Baffles (115)(125) may be provided inside the housingsor vessels (111)(121) of the preheater (10) and the thermaldecomposition device or the pyrolyzer (20).

More specifically, as shown in FIG. 7 , the preheater (10) comprises apreheater vessel (111); a preheater baffle (115) with the front surfaceprovided within the preheater vessel (111); and a preheater outlet (119)for discharging the heat carriers (30). The heat carriers (30)discharged from the preheater outlet (119) is fed to the pyrolyzer (20)from the top of the pyrolyzer (20) into the interior of the pyrolyzer(20). The pyrolyzer (20) is provided below the preheater outlet (119).The heat carriers (30) will be fed from the top of the pyrolyzer (20).The gap marked G is provided between the interior side walls of thepreheater vessel (111) and the preheater baffle (115). The heat carriers(30) fall downwards through the gap marked G.

Also, as shown in FIG. 8 , the pyrolyzer (20) comprises a pyrolyzervessel (121); a pyrolyzer baffle (125) with a front surface providedwithin the pyrolyzer vessel (121); and a pyrolyzer outlet (129) fordischarging the heat carriers (30), which is provided below thepyrolysis vessel (121). A gap marked G is provided between the interiorside walls of the pyrolyzer vessel (121) and the pyrolyzer baffle (125).The heat carriers (30) fall downwards through the gap marked G.

The heat carriers (30) discharged from the pyrolyzer outlet (29) isreturned to the discharge treatment section (240) and through thecirculation section (290). The heat carriers (30) are then re-introducedto the preheater (10), which is located at the top (see FIG. 1 ).

In addition, unlike the configurations shown in FIGS. 7 and 8 , pipesections (131)(141), through which the heat carriers (30) pass through,may be provided on the interior side walls of the vessels (111)(121).

More specifically, as shown in FIG. 9 , a preheater pipe section (131)is provided on the interior side walls of the preheater vessel (111) forthe heat carriers (30) to pass through. By passing through the preheaterpiping section (131), the heat carriers (30) may be supplied to thepyrolyzer (20), from the top, provided below the preheater.

Moreover, as shown in FIG. 10 , a pyrolyzer pipe section (141) isprovided on the interior side walls of the pyrolyzer vessel (121) forthe heat carriers (30) to pass through. By passing through the pyrolyzerpipe section (141), the heat carriers (30) may be supplied to thedischarge treatment section (240), from the top, provided below thepyrolyzer.

Furthermore, even when the pipe sections (131)(141) are provided, asshown in FIGS. 9 and 10 , the vessels (111)(121) may still be providedwith baffles (115)(125).

The pyrolyzer (20) and/or preheater (10), which comprises of the upperbodies (111 a)(121 a) and the bottom cone-shaped lower bodies (111b)(121 b) serve as vessels for a moving bed. After the heat carriers(30) in the upper bodies (111 a)(121 a) moved laterally outwards fromthe bottom of the upper bodies (111 a)(121 a) towards the upper part ofthe lower bodies (111 b)(121 b), the heat carriers (30) move down alongthe walls of the lower bodies (111 b)(121 b). The lower bodies (111b)(121 b) may have a structure that allows the discharge of the heatcarriers (30) from the lower bodies (111 b)(121 b).

In the pyrolyzer (20) located below the preheater (10) in the biomassgasification device described in the present embodiment, the upperportion (top portion), preferably at the top-most portion, is providedwith an inlet (127) for the heat carriers (30) (see FIG. 1 ) and adischarge outlet for the heat carriers (30) (see FIG. 2 ) at the lowerportion (bottom portion), preferably at the bottom-most portion (thisoutlet constitutes the pyrolyzer outlet (129)). Above the inlet (127)for the heat carriers (30) and below the discharge outlet (129), as anexample, a so-called two-stage valve system may be provided consistingof two valves, one each for the upper and lower section of the piping.

More specifically, as shown in FIG. 11 , the first valve (50) may beprovided between the preheater (10) and the pyrolyzer (20). This firstvalve system (50) may have an adjusting/tuning component, a firstopen/close component below the adjusting component, and a secondopen/close component below the first open/close component. A controlunit (100) may control the opening and closing of the component asfollows: the first open/close component to be open while the secondopen/close component is closed; and the second open/close component tobe open while the first open/close component is closed. Each of thefirst and second open/close components may be a damper valve. In thesucceeding descriptions, the first open/close component is the firstdamper valve (51 a) and the second open/close component is the seconddamper valve (51 b). A situation in which the adjusting/tuning componentof the first valve system (50) is a swing valve (52) may also beconsidered.

Consider the first-set of the two top and bottom damper valves (51 a)and (51 b) to be in close position. First, the upper first damper valve(51 a) is opened to allow the heat carriers to drop and flow through thepiping. The heat carriers then fill the space between the second dampervalve (51 b) and the first damper valve (51 a). Next, the first dampervalve (51 a) is closed, and the second damper valve (51 b) is opened.The heat carriers that were filling the space between the second dampervalve (51 b) and the first damper valve (51 a) is introduced into thepyrolyzer (20), or withdrawn from the pyrolyzer (20). By repeating thesevalve operations, the heat carriers are almost continuously introducedinto and almost continuously withdrawn from the pyrolyzer (20). Thisintroduction and withdrawal method is an example and the method that maybe considered in this embodiment is not limited to this method.

In the present embodiment, a second set of valves (90) between thepyrolyzer (20) and the discharge treatment section (240) may beprovided. The second set of valves (90) may have a pair of damper valves(91 a)(91 b) and a swing valve (92), which is an example of anadjusting/tuning section. Similar to the first set of valves (50), thesecond set of valves (90) may also have a swing valve (92), a firstdamper valve (91 a) and second damper valve (91 b), which may bearranged in order, from top to bottom. As shown in FIG. 1 , thedischarge treatment section (240) is equipped with a filter (F). Sootcontained in the biogas is filtered (F) and falls downward through thefilter (F). The heat carriers (30) that do not pass through the filter(F) is re-circulated through the circulation section (29), whichconsists of configurations such as an elevator type, an escalator type,etc. After going through the circulation section (29), the heat carriers(30) are then fed back into the preheater (10).

Most of the heat required for the pyrolysis of biomass in the pyrolyzer(20) is provided by the heat possessed by the heat carriers (30), whichare preheated to the temperatures described previously.

The preheater (10) is preferably installed above the pyrolyzer (20),where all of the heat carriers (30) can be heated to a predeterminedtemperature. The preheated heat carriers (30) can then be fed to thepyrolyzer (20).

The pyrolyzer (20) and/or the preheater (10) is/are installed in theupper bodies (111 a)(121 a) and the cone-type lower bodies (111 b)(121b) and the heat carriers (30) in the upper bodies (111 a)(121 a). Theheat carriers (30) in the upper bodies (111 a)(121 a) are transportedlaterally from the bottom of the upper bodies (111 a)(121 a) to theouter rim of the lower bodies (111 b)(121 b), and moves down along thewalls of the lower body (111 b)(121 b). The structure may be configuredto enable discharge of the heat carriers (30) from the bottom of thelower bodies (111 b)(121 b) to the outside.

The above features of the pyrolyzer (20) described solve the problems ofconventional moving beds, in which even if the volume is designed togasify a certain amount of biomass, only a small volume in the centerwhere the heat transfer medium moves can be effectively gasified. Inthis embodiment, the problem that the preheater (10) does not allow thepreheated heat carriers (30) to move smoothly to the pyrolyzer (20) canbe solved, and the volume can be used effectively and evenly.

More specifically, by moving the heat carriers (30) so that it isdischarged in the circumferential direction, as it does in thisembodiment, the heat carriers (30) could fall uniformly in the plane ata uniform speed (see FIGS. 2, 4, and 5 ). FIG. 3 shows the configurationwithout the baffle used in this study. In this configuration, theprofile of the black-colored heat carriers (30) is curved that protrudesdownward. The heat carriers (30) around the center can easily falltowards the bottom, which is unlike the heat carriers (30) around theperiphery. This results in differences in the movement characteristicsof each of the heat carriers (30) and we were able to confirm this. Onthe other hand, when the vessels (111)(121) are provided with thebaffles (115)(125) inside the vessels (111)(121), as shown in FIGS. 2,4, and 5 , the black-colored heat carriers (30) moved downward whileremaining horizontal, which confirms uniformity in the downward movementof the heat carriers (30).

There are no restrictions on the geometry of the upper bodies (111a)(121 a), as long as the heat carriers (30) can move to the lower body.However, cylindrical and rectangular shapes are preferred.

There are no restrictions on the geometry of the lower bodies (111b)(121 b), as long as the heat carriers (30) can be discharged at thebottom. However, inverted conical and inverted trapezoidal shapes arepreferred.

The cross-section of the lower end of the upper bodies (111 a)(121 a)may be smaller than the cross-section of the upper end of the lowerbodies (111 b)(121 b). If the cross-section is circular in shape, thelower end of the upper bodies (111 a)(121 a) diameter may be smallerthan the diameter of the upper end of the lower bodies (111 b)(121 b).The lower bodies (111 b)(121 b) may be smaller. The top surface of theupper end of the lower bodies (111 b)(121 b) and the bottom surface ofthe upper bodies (111 a)(121 a) are connected and has to be continuous.A connecting wall extending from the outermost portion of (111 b)(121 b)to the lower end of the upper bodies (111 a)(121 a) may be provided.

Moreover, it is also not limited to the described configuration, asshown in FIGS. 4 and 5 . The outer bodies (111 c)(121 c) and an upperbody (111 a)(121 a) within the outer body (111 c)(121 c) may beprovided. The area lower than the upper bodies (111 a)(121 a) in theouter bodies (111 c)(121 c) constitutes the lower bodies (111 b)(121 b).In FIGS. 4 and 5 , the lower bodies (111 b)(121 b) and the upper baffles(115)(125) are in the in-plane direction, and the lower baffles(115)(125) are in the vertical direction within the lower bodies (111b)(121 b). In some cases, the provision of baffles (115)(125) extendingin the vertical direction can also be used to facilitate the smooth flowof the heat carriers (30).

A baffle (115)(125) is provided below the lower end of the upper bodies(111 a)(121 a). The lower bodies (111 b)(121 b) may be provided aroundthe outer periphery of the baffles (115)(125). In this configuration,the lower end of the upper bodies (111 a)(121 a) and the barriers(115)(125) in the vertical direction, and an aperture (23) is formedbetween the lower end of the upper bodies (111 a)(121 a) and the baffles(see FIGS. 4 and 5 ). In addition, a gap (G) will be formed between thebaffles (115)(125) and the lower bodies (111 b)(121 b) in the in-planedirection. In this case, the heat carriers (30) that are in the upperbodies (111 a)(121 a) will go through the aperture (23). And then theheat carriers (30) will spread outwards from the upper bodies (111a)(121 a) and move through the gap (G) to the lower bodies (111 b)(121b).

The baffles (115)(125) may be installed at the center of the lowerbodies (111 b)(121 b). The in-plane centers of the upper bodies (111a)(121 a), lower bodies (111 b)(121 b), and baffles (115)(125) maycoincide. In this manner, the heat will be uniformly distributed in thein-plane direction. This is beneficial because it allows the heatcarriers (30) to flow uniformly in the in-plane direction.

The baffles (115)(125) are not limited to any particular shape, as longas they achieve the above purposes. When the lower bodies (111 b)(121 b)are inverted conical or inverted conical trapezoidal in shape, thebaffles (115)(125) installed in the upper bodies (111 a)(121 a) and inthe lower bodies (111 b)(121 b) may have the following preferred shapes:conical, inverted conical, and coma-shaped.

The front surface (top surface in this embodiment) of the baffles(115)(125) may be positioned such that the central region is higher thanthe peripheral region. A sloping surface may be provided between thecentral region and the peripheral regions. As an example, a conical (seeFIG. 6 a ) or tangential conical baffle (115)(125) may be provided. Inthis arrangement, the heat carriers (30) will be properly dischargedinto the lower bodies (111 b)(121 b) (see FIG. 6 a ).

Moreover, the back surface of the baffles (115)(125) (the bottom surfacein this embodiment) may be positioned such that the central region islower than the peripheral region. It may be positioned in a position sothat a sloping surface is provided between the central region and theperipheral region. As an example, a conical (see FIG. 6 b ) ortangential conical baffle (115)(125) may be provided. In thisarrangement, the central portion of the baffle (115)(125) is thicker,and thus more resistant to bending stresses induced by the flow of theheat carriers (30)(see FIG. 6B).

The configurations presented in FIGS. 6 a and 6 b may be combined. As anexample, the coma-shaped baffles (115)(125) shown in FIG. 6 c may beemployed. In this arrangement, the combination of the configurationsshown in FIGS. 6 a and 6 b were used (see FIG. 6 c ).

Furthermore, note that when the shapes of the lower bodies (111 b)(121b) are pyramidal, the baffles installed between the upper bodies (111a)(121 a) and the lower bodies (111 b)(121 b) are preferred to bepyramidal, inverted pyramidal, or its combination (115)(125).

In the conical, inverted conical, and coma-shaped baffles (115)(125),the heat carrier (30) flows along the baffles installed in the lowerbodies (111 b)(121 b) as indicated by the arrows shows in FIGS. 6A, 6B,and 6C, before it is discharged from the lower bodies (111 b)(121 b).

As shown in FIG. 12 , the main bodies (115 a)(125 a) of the baffles(115)(125) within the vessels (111)(121) may be provided with aplurality of securing members (130) to secure the baffle to the interiorsidewalls of the vessels (111)(121). The gap between the fixing members(130) may then be a gap (G) for the heat carriers to pass through.

The main bodies (115 a)(125 a) of the baffles (115)(125) within thevessels (111)(121) may be disk-shaped (see FIG. 12 ). The main bodies(115 a)(125 a) of the baffles (115)(125) may be secured within thevessels (111)(121) by means of fixing members (130) provided between theinner sidewalls of the vessels (111)(121). As shown in FIGS. 7 and 8 ,the main bodies (115 a)(125 a) of the baffles (115)(125) may also besecured to the vessels (111)(121) using the fixing members (130) locatedon the back side (bottom portion) of the main bodies (115 a)(125 a) ofthe baffles (115)(125).

This form of the system may be incorporated into a conventional biomassgasification device.

The biomass gasification device described in this embodiment includes apyrolyzer (20) which has a biomass feed inlet with a non-oxidizing gasfeed inlet and/or a steam inlet in line. The pyrolysis gas reformer (40)has a steam inlet and a reformed gas outlet. The pyrolysis gas generatedin the pyrolyzer (20) is introduced to the pyrolysis gas reformer (40).Piping (200) between the pyrolyzer (20) and the pyrolysis gas reformer(40) that is used to introduce the pyrolysis gas from the pyrolyzer (20)to the pyrolysis gas reformer (40) as described above is provided. Thepyrolyzer (20) and pyrolysis gas reformer (40) are each equipped with aninlet and outlet for a preheated heat carriers to perform pyrolysis ofbiomass and reforming of pyrolysis gas generated by pyrolysis of biomassusing the heat from the heat carriers. The pyrolyzer (20) and pyrolysisgas reformer (40) are installed in parallel to the flow of the heatcarriers. The pyrolysis gas inlet pipe (200) is provided on both sidesof the pyrolyzer (20) and the pyrolysis gas reformer (40), below thesurface of the heat carrier bed or layer formed in the pyrolyzer (20)and the pyrolysis gas reformer (40). The pyrolysis gas inlet pipe (200)is installed perpendicularly to the direction of gravity. The pyrolyzer(20) and/or a preheater (10) has a moving bed of heat carriers (30) inthe upper bodies (111 a)(121 a) and the bottom cone-shaped lower bodies(111 b)(121 b). The heat carriers (30) in the upper bodies (111 a)(121a) are moved laterally from the bottom of the upper bodies (111 a)(121a), along the wall of the lower bodies (111 b)(121 b), and thendischarged from the bottom of the lower bodies (111 b)(121 b).

Moreover, the pyrolyzer (20) has a biomass feed inlet with anon-oxidizing gas feed inlet and/or a steam inlet in line. The pyrolysisgas reformer (40) has a steam inlet and a reformed gas outlet. Piping(200) between the pyrolyzer (20) and the pyrolysis gas reformer (40)that is used to introduce the pyrolysis gas from the pyrolyzer (20) tothe pyrolysis gas reformer (40) as described above is provided. Thepyrolyzer (20) is further provided with an inlet and outlet for thepreheated heat carriers to perform pyrolysis of the biomass by the heatcoming from the heat carriers. Furthermore, the pyrolysis gas reformer(40) performs steam reforming of the pyrolysis gas generated by thepyrolysis of biomass. The pyrolysis gas reformer (40) is furtherequipped with an air or oxygen inlet to perform steam reforming bypartial oxidation of the pyrolysis gas generated by the pyrolysis of thebiomass with the air or oxygen. A pyrolysis gas inlet pipe (200) isprovided on the side of the pyrolyzer (20) below the surface of the heatcarrier bed or layer formed in the pyrolyzer (20). The pyrolyzer (20)and/or the preheater (10) is equipped with the upper bodies (111 a)(121a) and the bottom cone-shaped lower bodies (111 b)(121 b). The heatcarriers (30) in the upper bodies (111 a)(121 a) are moved laterallyfrom the bottom of the upper bodies (111 a)(121 a), along the wall ofthe lower bodies (111 b)(121 b), and then discharged from the bottom ofthe lower bodies (111 b)(121 b).

In another form of this embodiment, the biomass gasification deviceconsists of a pyrolyzer (20) in which biomass is heated in anon-oxidizing gas atmosphere or in a mixed gas atmosphere ofnon-oxidizing gas and steam; a pyrolysis gas reformer (40) in which thegas generated in the above pyrolyzer (20) is reformed in the presence ofsteam; and preheated heat carriers (30) that are fed from the pyrolyzer(20). The heat of the heat carriers (30) is used to reform the gas fromthe pyrolyzer (20) in the presence of steam. The pyrolysis of thebiomass is performed, and then the pyrolysis gas generated by thepyrolysis of the biomass is introduced into the pyrolysis gas reformer(40) to perform steam reforming of the pyrolysis gas. The pyrolysis gasgenerated by the pyrolysis of the biomass is introduced into thepyrolysis gas reformer (40) through the pyrolysis gas inlet pipe. Thepyrolysis gas is introduced into the pyrolysis gas reformer (40). At thesame time, the pyrolysis gas is partially oxidized by air or oxygenintroduced into the pyrolysis gas reformer (40). In the pyrolyzer (20)and/or preheater (10) consisting of the upper bodies (111 a)(121 a) anda bottom cone-shaped lower bodies (111 b)(121 b), the heat carriers (30)in the upper bodies (111 a)(121 a) are moved laterally from the bottomof the upper bodies (111 a)(121 a), along the wall of the lower bodies(111 b)(121 b), and then discharged from the bottom of the lower bodies(111 b)(121 b).

An example of this mode of operation is described below.

The heat carriers (30) are preheated in the preheater (10) before beingintroduced into the pyrolyzer (20). The heat carriers (30) arepreferably heated to 650-800° C., more preferably 700-750° C. The lowerlimit (i.e., below 650° C.) may lead to the biomass (e.g., high ashbiomass) not sufficiently pyrolyzed in the pyrolyzer (20), resulting toa decrease in the amount of the pyrolysis gas generated. On the otherhand, if the temperature exceeds the upper limit (i.e., 800° C.),volatilization of phosphorus and potassium may occur, resulting inblockage and corrosion of piping due to the formation of diphosphoruspentoxide and potassium pentoxide. In addition, it only gives off extraheat, and no significant increase in effectiveness can be expected,which in turn only leads to higher cost. It also leads to a decrease inthe thermal efficiency of the device.

The heat carriers (30) heated to a predetermined temperature in thepreheater (10) is then introduced into the pyrolyzer (20). In thepyrolyzer (20), the heat carriers (30) are brought into contact with thebiomass supplied to the pyrolyzer (20) via the biomass feed inlet (220).Contact between the heat carriers (30) and the biomass causes thebiomass to be heated and pyrolyzed, producing pyrolysis gas. Thegenerated pyrolysis gas passes through the pyrolysis gas introductionpipe (200) and is introduced into the pyrolysis gas reformer (40). Atthis point, tar, dust, and other particles contained in the generatedpyrolysis gas are captured by the heat carriers (30). With tar and otherparticulates (soot, dust, etc.) adhering to the heat carriers (30), theheat carriers (30) are then discharged from the bottom of the pyrolyzer(20) leading to removal of most of the adhered tar and particulates.

The pyrolyzer (20) and/or preheater (10), which comprises of the upperbodies (111 a)(121 a) and the bottom cone-shaped lower bodies (111b)(121 b) serves as the vessel for a moving bed. The heat carriers (30)introduced from the preheater (10) into the pyrolyzer (20) first entersthe upper bodies (111 a)(121 a) of the pyrolyzer (20). The heat carriers(30) pass laterally through the upper bodies (111 a)(121 a) and passthrough the opening of the lower body (23). The heat carriers (30) thenpass through the baffle between the upper bodies (111 a)(121 a) and thelower bodies (111 b)(121 b), and move towards the lower bodies (111b)(121 b).

Heat carriers (30) are introduced into the lower bodies (111 b)(121 b)along the walls of the lower bodies (111 b)(121 b) and moves to thebottom of the lower bodies (111 b)(121 b). The heat carriers (30) aredischarged from the bottom of the lower bodies (111 b)(121 b).

Within the lower bodies (111 b)(121 b), a baffle (115)(125) is providedin the center portion, which facilitate the movement of the heatcarriers (30) to the bottom of the lower bodies (111 b)(121 b). Thesebaffles (115)(125) allow the heat carriers (30) to move towards thebottom of the lower bodies (111 b)(121 b), preventing them from stayingin the interior of the lower bodies (111 b)(121 b).

By controlling the introduction of the heat carriers (30) into thepyrolyzer (20) and the withdrawal rate of the heat carriers (30) fromthe pyrolyzer (20), the thickness of the layer or the height of the bedof the heat carriers (30) can be controlled to the appropriate value,while also allowing the temperature of the pyrolyzer (20) to becontrolled to the predetermined temperature described above. In thismanner, the heat carriers (30) are introduced only in the pyrolyzer(20), and the heat is used for the pyrolysis of the biomass, while thepyrolysis gas reformer (40) is controlled through the introduction ofsteam and oxygen (or air). The process thereby makes it possible tocontrol the internal temperatures of the pyrolyzer (20) and pyrolysisgas reformer (40) separately. This enables the reforming reaction in thepyrolysis gas reformer (40) to proceed at an appropriate temperature. Inparallel, the pyrolysis of biomass in the pyrolyzer (20) can be carriedout at an appropriate temperature.

The residence time of the biomass in the pyrolyzer (20) is preferablyfrom 5 to 60 minutes, more preferably from 10 to 40 minutes, and evenmore preferably from 15 to 35 minutes. Below the lower limit (i.e., 5minutes), heat is not uniformly transferred to the biomass and pyrolysiscannot uniformly conducted, resulting in a reduction in the amount ofpyrolysis gas generated. On the other hand, even if the upper limit (60minutes) is exceeded, no significant increase in pyrolysis can beobserved. In fact, the equipment cost will increase. Here, the residencetime of the biomass in the pyrolyzer (20) can be appropriately adjustedvia the flow rate of the heat carriers (30) and the biomass feed rate.

When the pyrolysis gas reformer (40) and the pyrolyzer (20) areconnected in series, the residence time in each vessel (i.e., theresidence time for biomass pyrolysis in the pyrolyzer (20) and theresidence time for decomposition of tar in the pyrolysis gas) are bothconsidered. It was impossible to control the residence time required forthe reforming reaction between pyrolysis gas and steam in the pyrolysisgas reformer (40) separately. The pyrolysis gas reformer (40) is heatedby introducing steam and oxygen or air separately, and the pyrolysis gasis heated by partial oxidation of the pyrolysis gas. By using a systemin which the pyrolysis gas is heated by partial oxidation of thepyrolysis gas, the residence time in each of the pyrolyzer (20) and thepyrolysis gas reformer (40) can be controlled independently.

As described above, the heat carriers (30) that have passed through thepyrolyzer (20) are discharged from the bottom of the pyrolyzer (20)together with the pyrolysis residue (char) of the biomass, and a smallamount of tar and dust that remain attached to the heat carriers (30).Treatment of the discharged heat carriers (30) is carried out byconventionally known methods, such as separation of char in thedischarge treatment section. The treated heat carriers (30) arerecirculated to the preheater (10) to be supplied again to the pyrolyzer(20).

In the pyrolysis gas reformer (40), the pyrolysis gas generated bypyrolysis of biomass in the pyrolyzer (20) is introduced through thepyrolysis gas inlet pipe (200). The pyrolysis gas introduced into thepyrolysis gas reformer (40) is partially oxidized by air or oxygen,thereby heating the internals of the pyrolysis gas reformer (40). Thisallows the pyrolysis gas to react with steam to reform the pyrolysis gasinto a hydrogen-rich gas.

The following examples will explain this embodiment in more detail, butthis embodiment is not limited by these examples.

Examples of the Embodiment

The biomass feedstock used in the example, and the gasifier used forpyrolysis of the biomass feedstock and pyrolysis gas reforming are asfollows.

Sewage sludge was granulated and used as the biomass feedstock. Themaximum size of the granulated sewage sludge was in the range of 6 to 15mm. The properties of the sewage sludge are shown in Table 1. Thecomposition of the ash obtained by combusting the sewage sludge areshown in Table 2.

TABLE 1 Component Value Proximate analysis Moisture 20.0% (by wt.) Ash16.0% (by wt.) Volatile matter 76.7% (by wt.) Fixed carbon 7.3% (by wt.)Elemental analysis C 36.10% (by wt.) H 5.98% (by wt.) O 35.09% (by wt.)N 5.26% (by wt.) S <1.35% (by wt.) Cl <0.22% (by wt.) Higher HeatingValue 16.9 MJ/kg

For the data presented in Table 1: Moisture, volatile matter, and fixedcarbon content were analyzed in accordance with JIS M8812. Ash contentwas analyzed in accordance with JIS Z7302-4: 2009. Higher Heating Value(HHV) was analyzed in accordance with JIS M8814. Carbon (C), hydrogen(H), and nitrogen (N) were analyzed in accordance with JIS Z7302-8:2002. Sulfur (S) was analyzed in accordance with JIS Z7302-7:2002. Chlorine (Cl) was analyzed in accordance with JIS Z7302-6:1999. Oxygen (O) was determined by subtracting the sum of themass percentages of C, H, N, S, Cl, and ash from 100. Ash, volatilematter, fixed carbon, and the elemental composition were all calculatedon a dry basis. Moisture content was measured at the time of collectionof the raw biomass material (sewage sludge).

TABLE 2 Component Value Silicon dioxide 25.60% (by wt.) Aluminum oxide17.00% (by wt.) Ferric oxide 14.90% (by wt.) Magnesium oxide 3.17% (bywt.) Calcium oxide 9.01% (by wt.) Sodium oxide 0.81% (by wt.) Potassiumoxide 1.49% (by wt.) Diphosphorus pentoxide 20.70% (by wt.) Mercury<0.005 mg/kg Chromium 200 mg/kg Cadmium 3 mg/kg Copper oxide 2400 mg/kgLead oxide 110 mg/kg Zinc oxide 0.38% (by wt.) Manganese oxide 0.24% (bywt.) Nickel 120 mg/kg

For the data presented in Table 2: silicon dioxide, aluminum oxide,ferric oxide, magnesium oxide, calcium oxide, sodium oxide, potassiumoxide, diphosphorus pentoxide, and manganese oxide were analyzed inaccordance with JIS M8815. Mercury, chromium, cadmium, copper oxide,lead oxide, zinc oxide, and nickel were analyzed in accordance with JISZ 7302-5:2002.

The gasifier basically consists of a pyrolyzer (20), a pyrolysis gasreformer (40), and a preheater (10) (see FIG. 1 ). The pyrolyzer (20)and pyrolysis gas reformer (40) are connected by a pyrolysis gas inputpipe (200) that introduces the pyrolysis gas generated in the pyrolyzer(20) into the pyrolysis gas reformer (40).

In this embodiment, a preheater (10) is provided above the pyrolyzer(20). The preheater (10) preheats the heat carriers (30) supplied to thepyrolyzer (20). The preheater (10) preheats the heat carriers (30) to befed to the pyrolyzer (20), and the heated heat carriers (30) are fed tothe pyrolyzer (20). The preheated heat carriers (30) are fed to thepyrolyzer (20) to provide the heat necessary for the pyrolysis of thebiomass. The heat carriers are then discharged from the bottom andrecirculated to the preheater (10). On the other hand, the pyrolysis gasgenerated in the pyrolyzer (20) is introduced through the pyrolysis gasinlet pipe (200) to the pyrolysis gas reformer (40).

In this embodiment, air or oxygen is separately introduced into thepyrolysis gas reformer (40) through the air or oxygen inlet pipes(261)(262). The introduction of air or oxygen causes partial oxidationof the pyrolysis gas. Steam is simultaneously introduced through steaminlet (242). The pyrolysis gas is reformed by steam, and the resultingreformed gas is discharged via the reformed gas outlet (230).Alternatively, air or oxygen, and steam can also be introduced throughthe air or oxygen inlet pipe (262) and steam inlet pipe (243) providedwith the pyrolysis gas inlet pipe (200). All the air or oxygen, andsteam can be introduced through the provided air or oxygen inlet pipes(261)(262) and the steam inlet pipes (242)(243).

The inner diameter of the straight body portion of the pyrolyzer (20) isabout 550 mm. The height is about 1100 mm. And the internal volume isabout 260 liters. On the other hand, the inner diameter of the straightbody portion of the pyrolysis gas reformer (40) is about 600 mm. Theheight is about 1200 mm. And the internal volume is about 360 liters.

Moreover, the pyrolysis gas inlet pipe (200) is provided on the side ofthe pyrolyzer (20), below the top surface of the bed of heat carriersformed in the pyrolyzer (20). On the other hand, for the pyrolysis gasreformer (40), the pyrolysis gas inlet pipe (200) is provided on theside of the pyrolysis gas reformer (40), below the top surface of thebed of heat carriers formed in the pyrolysis gas reformer (40). Thepyrolysis gas inlet pipe (200) is provided on the side near the bottomof the vessel. The pyrolysis gas inlet pipe (200) is providedhorizontally, or perpendicular to the direction of gravity. Thepyrolysis gas inlet pipe (200) has a length of about 1000 mm and aninner diameter of about 80 mm. The inside of the pipe is covered withheat insulating material, and the protruding portion is also coveredwith a heat insulating material. The heat carriers (30) are approximatespheres with a diameter (maximum diameter) of 10 to 12 mm. Alumina isused as the material for the heat carriers (30).

The interiors of the pyrolyzer (20) and the preheater (10) arepre-filled with heat carriers (30) to a height of about 70% of therespective vessels. The heat carriers (30) are then heated in thepreheater (10) to a temperature of about 700° C. Then, the heat carriers(30) are introduced to the pyrolyzer (20), from the top of the pyrolyzer(20), at a rate of 200 kg/h. The appropriate amount of heat carriers(20) is withdrawn from the bottom of the pyrolyzer (20), and thecirculation of the heat carriers (30) is started.

The circulation of the heat carriers (30) gradually raises thetemperature of the gas phase inside the pyrolyzer (20), and thetemperature of the vessel itself. While continuing the describedcirculation of the heat carriers (30), the temperature of the heatcarriers (30) inside the preheater (10) is gradually raised to 800° C.After reaching this temperature, the circulation of the heat carriers(30) is continued to gradually increase the temperature of the gas phaseinside the pyrolyzer (20). The temperature of the gas phase in thepyrolyzer (20) is increased to 550° C. When the temperature of the gasphase in the pyrolyzer (20) exceeds 550° C., raw biomass material,nitrogen gas, and steam are introduced from the raw biomass materialfeed inlet port (220), non-oxidizing gas inlet port (250), and steaminlet port (241), respectively. The temperature of the pyrolyzer (20) iscontrolled to be at 600° C.

At this time, the heat carriers (30) are deposited forming beds in thepyrolyzer (20). The deposited amount is about 60% of the volume of thepyrolyzer (20). The amount of the heat carriers (30) withdrawn from thepyrolyzer (20) is the same as the feed rate to the pyrolyzer (20), whichis 200 kg/h. The temperature of the heat carriers (30) at the time ofwithdrawal is 650° C. However, the amount of the heat carriers (30)withdrawn from the pyrolyzer (20) can be controlled depending on thetemperature conditions.

In the operation described above, sewage sludge as raw biomass material(biomass feedstock) is fed into a metered feeder. The raw biomassmaterial (biomass feedstock) is continuously introduced into thepyrolyzer (20) from the biomass feed inlet (220) using a feed rate ofabout 22 kg/h (dry basis).

The temperature of the pyrolyzer (20) gradually decreases as the rawbiomass material (biomass feedstock) is introduced. At the same time,nitrogen gas and superheated steam are introduced into the pyrolyzer(20) while adjusting the feedstock supply rate. The temperature of thepyrolyzer (20) is maintained at 600° C. and the pressure in thepyrolyzer (20) is maintained at 101.3 kPa.

In this process, nitrogen gas is introduced through the non-oxidizinggas inlet (250) that located at the top of the pyrolyzer (20), at afinal rate of 1000 liters/h at a constant volume. The steam used issuperheated (160° C., 0.6 MPa). The steam is introduced at a finalconstant rate of 1 kg/h via the steam inlet (241) located at the top ofthe pyrolyzer (20). The residence time of the raw biomass material(biomass feedstock) in the pyrolyzer (20) is about 1 h. This results in15 kg/h of gas produced by pyrolysis in the pyrolyzer (20). In addition,a total of 6.5 kg/h of char and ash are discharged as pyrolysis residuevia the pyrolysis residue (char) outlet (210).

The pyrolysis gas obtained in the pyrolyzer (20) is subsequentlyintroduced into the pyrolysis gas reformer (40) through the pyrolysisgas inlet pipe (200) from the lower side of the pyrolyzer (20).

Although the temperature in the pyrolysis gas reformer (40) becomesunstable when the pyrolysis gas is first introduced, by adjusting theamount of superheated steam introduced through the steam inlet (242),and the amount of oxygen introduced from the air or oxygen inlet (261),the pyrolysis gas is partially oxidized and the temperature inside thepyrolysis gas reformer (40) reaches 1000° C. The temperature inside thepyrolysis gas reformer (40) is adjusted so that the temperature insidethe pyrolysis gas reformer (40) reaches 1000° C. At this time, thepyrolysis gas reformer (40) is maintained at a pressure of 101.3 kPa.The superheated steam from the steam inlet (242) provided at the bottomof the pyrolysis gas reformer (40) is introduced at a final constantvolumetric rate of 3.7 kg/h. Oxygen from the air or oxygen inlet (261)is introduced at a final constant volumetric rate of 2.3 Nm³/h. However,this amount of oxygen is increased or decreased according to the actualdegree of temperature increase inside the pyrolysis gas reformer (40).

In the operation described above, the pyrolyzer (20) is maintained at atemperature of 600° C. and a pressure of 101.3 kPa. The pyrolysis gasreformer (40) is maintained at a temperature of 950° C. and a pressureof 101.3 kPa. As a result of this process, reformed gas, at atemperature of 1000° C., is obtained from the reformed gas outlet (230)at a rate of 31 kg/h.

The produced reformed gas is collected in a rubber bag and the gascomposition is analyzed by gas chromatography. Table 3 shows thecomposition of the collected reformed gas. The operation can be carriedout for 3 consecutive days. During the operation period, continuousoperation can be maintained without difficulties (e.g., problems causedby tar). Moreover, during the operation period, there were no problemscaused by blockage of the heat carriers (30) in the pyrolysis gas inletpipe (200) due to tar accumulation, etc. Smooth introduction of thepyrolysis gas from the pyrolyzer (20) to the pyrolysis gas reformer (40)was maintained. The amount of tar in the reformed gas taken from theoutlet of the pyrolysis gas reformer (40) was about 10 mg/Nm³.

TABLE 3 Component Value H₂ 53.9% (by vol.) CO 26.9% (by vol.) CO₂ 15.4%(by vol.) CH₄ 0.3% (by vol.) HCl 0.04% (by wt.) H₂S 0.46% (by wt.) N₂3.0% (by wt.)

The reformed gas can be obtained in this manner. With the stable andcontinuous supply of the heat carriers (30) in the gasifier, thepressure fluctuations in the pyrolyzer (20) were reduced which alsosolves the problem of reduced gas separation capacity, thereby providinggas of stable quality.

Potential for Industrial Application

In the biomass gasifier described, the heat carriers (30) in thepyrolyzer (20) and/or preheater (10) move laterally from the bottom ofthe cylindrical body to the outer side of the upper bodies (111 a)(121a), and then move down along the walls of the lower bodies (111 b)(121b) to its bottom from where the heat carriers (30) are discharged. Thismechanism enables effective utilization of the full volume allowingefficient biomass pyrolysis.

This form of biomass gasification system is designed to convert biomass,preferably biomass with relatively high ash content, into reformed gascontaining a large amount of hydrogen and other valuable gases. Thesystem not only prevents blockage and corrosion of piping caused by thevolatilization of diphosphorus pentoxide and potassium contained in theash component of the biomass, but also suppresses N₂O generation andreduces tar and soot generation. Therefore, it is expected to be used asa gasifier for biomass, especially biomass with relatively high ashcontent, in the future.

EXPLANATION OF SIGNS

-   10 Preheater (temporary holding section)-   20 Pyrolyzer (temporary holding section)-   30 Heat carriers-   40 Pyrolysis gas reformer-   111 Preheater vessel-   121 Pyrolyzer vessel-   111 a, 121 a Upper bodies-   111 b, 121 b Lower bodies-   115, 125 Baffles-   119, 129 Discharge section-   131, 141 Piping

What is claimed is:
 1. A biomass gasifier comprising a temporary holdingsection for temporarily holding and discharging heat carriers, whereinthe temporary holding section has a vessel and an outlet for dischargingthe heat carriers, the biomass gasifier is provided with a baffle withinthe vessel that forms a gap for the heat carriers to pass through thespace between the main body of the baffle and the interior side walls ofthe vessel, or with a piping for the heat carriers to pass through onthe interior side walls of the vessel.
 2. The biomass gasifier accordingto claim 1, wherein the temporary holding section is a preheater thatpreheats the heat carriers, and the discharge section is the preheaterdischarge section, the heat carriers that were discharged from thepreheater bottom are fed to the pyrolyzer.
 3. The biomass gasifieraccording to claim 1, wherein the temporary holding section is apyrolyzer that receives a supply of heat carriers preheated in apreheater, the pyrolyzer performs pyrolysis of the biomass using theheat coming from the heat carriers, and the discharge section is thepyrolyzer discharge section, and the heat carriers that were dischargedfrom the pyrolyzer discharge section are fed to the preheater throughthe circulation section.
 4. The biomass gasifier according to claim 1,wherein the central region of the front face of the baffle is positionedhigher than the peripheral region, and a sloping surface is providedbetween the central region and the peripheral region.
 5. The biomassgasifier according to claim 1, wherein the back surface of the bafflehas a central region positioned lower than the peripheral region, and asloping surface is provided between the central region and theperipheral region.
 6. The biomass gasifier according to claim 1, whereina plurality of fixing members is provided between the main body of thebaffle and the interior side walls of the vessel to secure the main bodyof the baffle to the vessel, and wherein the gap between the fixingmembers is a gap for the heat carriers to pass through.
 7. The biomassgasifier according to claim 1, wherein the main body of the baffle isdisk-shaped, the main body of the baffle is attached to the vessel by aplurality of fixing members between the main body of the baffle and theinterior side wall of the vessel, or by a plurality of fixing members onthe back side of the main body.
 8. The biomass gasifier according toclaim 1, wherein the vessel has an upper body and a lower body below theupper body, the cross-section of the lower end of the upper body issmaller than the cross-section of the upper end of the lower body, abaffle is provided below the lower end of the upper body, and a gap isformed between the baffle and the lower body.